fuel tank help

I have a 70 Dart with a leaky fuel tank. Has a hole rusted in it and is not fixable. I have never taekn a fuel tank out and when I tried to loosed the tank strap bolts, I could not get them loose. They are rusted and I am afraid that I will break the brackets the straps hook to if I turn them any harder. I tried wd-40 etc, and they wont free up. Any suggestions would be appreciated.